Aluminum flux



United States Patent Office Patented June 1, 1965 3,186,881 ALUMINUM FLUX Frank E. Robbins, Midland, Mich, assignor to The Dow Chemical Company, Midland, Mich, a corporation of Delaware No Drawing. Filed July 2, 1962, Ser. No. 207,066 4 Claims. (Cl. 143-46) This invention relates to a novel flux for use with aluminum. More particularly, this invention relates to a flux composition containing inorganic halide salts.

When aluminum is melted in the presence of air, as in making aluminum alloys or preparing a melt for casting, a number of problems are usually encountered Among these problems are dross and slag formation which may cause a build up on the melt vessel walls with a consequent reduction in heat transfer, and a general contamination of the metal product. A problem related to the dross and slag formation is that of metal loss. A certain amount of the aluminum alloy is usually consumed in the formation of dross and slag. Fluxes are sometimes used in the melting of aluminum in an attempt to alleviate some of these problems.

Further, many commonly used fluxes do not operate well with aluminum alloys containing hypereutectic amounts of silicon. After melting with many of the ordinary fluxes, the structure of the hypereutectic alloy may lack continuity, with a corresponding loss of strength.

An object of this invention is to provide a flux which is compatible with aluminum alloys containing hypereutectic amounts of silicon.

Among the other objects of the present invention is the provision of a novel flux which will aid in preventing the formation of dross and slag, have good heat transfer properties, prevent deterioration of vessel linings, and remain liquid at aluminum melt temperature for extended periods of time.

The objects of the present invention may be accomplished by the use of a mixture of inorganic halide salts as a melting flux with aluminum.

As used herein, the term aluminum means aluminum or aluminum alloy containing at least seventy percent aluminum.

Fluxes useful in accordance with the present invention contain from about ten to about twenty percent by weight potassium chloride, from about fifty-five to about seventyfive percent by weight calcium chloride, from about five to about sixteen percent by weight barium chloride, and from about five to about twelve percent by weight calcium fluoride.

Specific combinations of the inorganic halide salts within the ranges above specified are generally to be determined by the desired flux melting point. It is desirable that the flux melt at about or slightly below the melting point of the aluminum to be melted. If the flux remains in a solid or granular state after the metal melts, the probability of oxidation of at least a portion of the molten metal is high.

The flux compositions of the present invention are useful over a range of temperatures from about the melting point of the specific combination used to very high temperatures, sometimes as high as 1800 degrees Fahrenheit, if desired.

Uses contemplated for the fluxes of the present invention with aluminum include, but are not limited to, foundry melting, secondary smelting, primary alloying and the like.

A typical charge to a melt vessel will usually contain from about two to about thirty percent by weight flux material and from about ninety-eight to about seventy percent by weight of the aluminum containing material to be melted. More or less flux may be used depending on the dictates of practice with the particular aluminum, the type of furnace, the shape of the melt vessel, the amount of impurities, the operating temperature to be used, and other like considerations involved in the metal melting art.

Fluxes of the present invention may be prepared as by blending solid inorganic halide salts in the desired combination. Another method of preparation is by fusing the desired combination of inorganic halide salts and grinding the fused mass to a desirable particle size. The latter method is generally to be preferred, particularly in situations where the flux melting point may be critical, and the presence of airborne fines is objectionable.

Flux compositions of the present invention are somewhat hygroscopic so that unless protected from the atmosphere they will usually acquire and retain water. Thus, it may be readily seen that care should be taken to store the fiuxe-s of the present invention in such a manner that they will remain dry.

A distinct advantage of the flux combinations of the present invention is their compatibility with aluminum containing a hypereutectic amount of silicon. Aluminum products of melts made using the flux combination of the present invention show good physical properties, i.e. good structural continuity and good strength.

Flux combinations of the present invention have a further advantage in that not only do they help prevent dross and slag formation, but they also aid in dissolving and removing old deposits of dross and slag which may have accumulated on the interior surface of the melt vessel. Because of the dark color of these fluxes, heat transfer in refractory type furnaces is greatly enhanced.

The present invention may be better understood in light of the following examples which are set forth to illustrate, but are not to be construed to limit, this invention.

Example 1 To a reverbratory furnace were charged about 9,000 pounds of 5005 aluminum having a nominal composition of 1.05 percent magnesium, and the balance aluminum, and 1800 pounds of flux containing fifteen percent potassium chloride, seventy percent calcium chloride, seven percent barium chloride, and eight percent calcium fluoride. The mixture was melted and observed over a twelve hour period. In this time, the flux provided a good liquid cover, and wetted and kept moist the refractory walls. When the melt 'was removed from the furnace, the refractory walls were observed to be clean and in good condition.

Example 2 Using a flux containing from about ten to about twenty percent by weight potassium chloride, from about fiftyfive to about seventy-fivepercent by weight calcium chloride, and from about to five to sixteen percent by weight barium chloride, and from about five to about twelve percent by weight calcium fluoride, aluminum and aluminum alloys may be melted for any of a variety of purposes. The fluxes will prevent excess slag and dross formation, and excessive loss of metal.

Example 3 When a flux as in Example 2 is used in the melting of an aluminum alloy containing a hyper eutectic amount of silicon, the alloy retains its structural integrity on cooling and has its expected good physical properties.

Various modifications may be made in the present invention without departing from the spirit or scope thereof, and itis to be understood that I limit myself only as defined in the appended claims. 7

I claim:

1. A flux composition adapted for use in melting aluminum and aluminum alloys in a melt vessel, said flux composition consisting essentially of from about ten to about twenty percent potassium chloride, from about fifty-five to about seventy-five percent calcium chloride, from about five to about sixteen percent barium chloride, and from about five to about twelve percent calcium fluoride.

2. A flux composition adapted for use in melting aluminum and aluminum alloys in a melt vessel, said flux composition consisting essentially of fifteen percent potassium chloride, seventy percent calcium chloride, seven percent barium chloride, and eight percent calcium fluoride. a

3. In a method of melting aluminum and aluminum alloys containing at least 70 percent aluminum in a melt vessel, the improvement which consists in providing a flux composition consisting essentially of from about to about 20 percent potassium chloride, from about 55 to about 75 percent calcium chloride, from about 5 to about 16 percent barium chloride, and from about 5 to about 12 percent calcium fluoride, adding said flux composition to the melt, and maintaing a molten layer of said flux composition in contact with the molten metal, thereby to substantially prevent formation of dross and slag.

4. In a method of melting aluminum and aluminum alloys containing at least percent aluminum in a melt vessel, the improvement which consists in providing a flux composition consisting essentially of about 15 percent potassium chloride, about 70 percent calcium chloride, about 7 percent barium chloride, and about 8 percent calcium fluoride, adding said flux composition to the melt, and maintaining a molten layer of said flux composition in contact with the molten metal, thereby to substantially prevent formation of dross and slag.

References Cited by the Examiner UNITED STATES PATENTS 2,170,863 8/39 Junker et a1. 93 2,327,065 4/43 Reirners 148-26 2,701,194 2/55 Deterding 75-194 FOREIGN PATENTS 560,636 4/44 Great Britain. 24,283 11/08 Great Britain.

DAVID L. RECK, Primary Examiner.

WINSTON A. DOUGLAS, Examiner. 

1. A FLUX COMPOSITION ADAPTED FOR USE IN MELTING ALUMINUM AND ALUMINUM ALLOYS IN A MELT VESSEL, SAID FLUX COMPOSITION CONSISTING ESSENTIALLY OF FROM ABOUT TEN TO ABOUT TWENTY PERCENT POTASSIUM CHLORIDE, FROM ABOUT FIFTY-FIVE TO ABOUT SEVENTY-FIVE PERCENT CALCIUM CHLORIDE, FROM ABOUT FIVE TO ABOUT SIXTEEN PERCENT BARIUM CHLORIDE, AND FROM ABOUT FIVE TO ABOUT TWELVE PERCENT CALCIUM FLUORIDE. 